WO2023188311A1 - Optical waveguide element, and optical modulation device and optical transmission device using same - Google Patents

Optical waveguide element, and optical modulation device and optical transmission device using same Download PDF

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Publication number
WO2023188311A1
WO2023188311A1 PCT/JP2022/016659 JP2022016659W WO2023188311A1 WO 2023188311 A1 WO2023188311 A1 WO 2023188311A1 JP 2022016659 W JP2022016659 W JP 2022016659W WO 2023188311 A1 WO2023188311 A1 WO 2023188311A1
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WIPO (PCT)
Prior art keywords
optical waveguide
optical
reinforcing member
substrate
adhesive layer
Prior art date
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PCT/JP2022/016659
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French (fr)
Japanese (ja)
Inventor
淳司 新井
祐美 村田
有紀 釘本
Original Assignee
住友大阪セメント株式会社
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Priority to PCT/JP2022/016659 priority Critical patent/WO2023188311A1/en
Publication of WO2023188311A1 publication Critical patent/WO2023188311A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/30—Optical coupling means for use between fibre and thin-film device
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 

Definitions

  • the present invention relates to an optical waveguide element, an optical modulation device using the same, and an optical transmitter, and particularly relates to an optical waveguide substrate including an optical waveguide, and an optical waveguide substrate disposed above the optical waveguide near the end of the optical waveguide.
  • the present invention relates to a reinforcing member, and an optical waveguide element in which the optical waveguide substrate and the reinforcing member are bonded via an adhesive layer.
  • optical waveguide elements such as optical modulators that use a substrate on which an optical waveguide is formed are often used.
  • optical waveguides are formed by thermally diffusing a high refractive index material such as Ti on a substrate with an electro-optic effect such as lithium niobate (LN), or by forming a rib-type structure (convex portion). Ru.
  • Input light is introduced from the outside or output light is led out to the optical waveguide substrate on which the optical waveguide is formed.
  • an input section of the optical waveguide is formed, and an optical block such as an optical fiber or a lens is connected to the end surface of the substrate.
  • optical blocks such as optical fibers, lenses, polarization combining means, reflecting means, etc. are connected to the end face of the substrate on which the output portion of the optical waveguide is formed, in order to properly guide the output light.
  • a reinforcing member is fixed onto the substrate along the end surface of the optical waveguide substrate with an adhesive (adhesive layer).
  • an adhesive adheresive layer
  • optical modulators are desired to be faster and smaller due to limitations in installation space. Therefore, it is necessary to form the optical waveguide of the optical waveguide element incorporated into the optical modulator with a rib-type structure and reduce the mold field diameter (MFD) of the light wave to about 1 ⁇ m. Since light confinement is strengthened by reducing the diameter, the bending radius of the waveguide can be reduced, and the optical waveguide element and optical modulator can be downsized.
  • MFD mold field diameter
  • the MFD of optical components such as optical fibers bonded to the optical waveguide end face of the optical waveguide element is approximately 10 ⁇ m, which is significantly different from the MFD of the optical waveguide (for example, 3 ⁇ m or less). Therefore, in order to suppress optical coupling loss, a spot size converter is disposed at the end of the optical waveguide element to increase the diameter of the MFD. Even when using a spot size converter, a reinforcing member (upper substrate) is placed along the end surface of the optical waveguide substrate in order to increase the bonding strength with optical components such as optical fibers that are bonded to the end of the optical waveguide element. .
  • the spot size converting section By selecting a material with a refractive index lower than that of the material constituting the spot size converting section as the adhesive for bonding the reinforcing member and the optical waveguide substrate, it is possible to arrange the spot size converting section around the spot size converting section.
  • the adhesive layer functions as a cladding layer of the spot size conversion section.
  • a reinforcing member When placing a reinforcing member in a part where an optical waveguide with a rib-type structure (hereinafter also referred to as a rib-type optical waveguide) or a spot size converter is arranged, since the optical waveguide with a rib-type structure protrudes from the optical waveguide substrate, It becomes difficult to attach the reinforcing member parallel to the optical waveguide substrate. Furthermore, the reinforcing member may be tilted, which may damage the optical waveguide, and the cladding layer of the spot size converter may be tilted, causing variations in the MFD.
  • Patent Document 1 proposes that a resin structure such as a resist that is higher than the spot size converter is placed so as to sandwich the spot size converter to suppress damage to the spot size converter and variations in the MFD. has been done. It is also disclosed that grooves are formed on the top surface of the structure to drain excess adhesive.
  • FIGS. 1 and 6 are diagrams showing the bonded state of the optical waveguide substrate (11) and the reinforcing member 2.
  • FIG. FIG. 2 shows a cross-sectional view taken along the dashed-dotted line A-A' in FIG. 1
  • FIG. 3 shows a cross-sectional view taken along the dashed-dotted line B-B' in FIG.
  • FIG. 5 shows a cross-sectional view taken along the dashed-dotted line A-A' in FIG. 4
  • FIG. 6 shows a cross-sectional view taken along the dashed-dotted line B-B' in FIG.
  • the thick dotted line frame 2 indicates the position where the reinforcing member is placed.
  • FIGS. 4 to 6 show the case where the adhesive layer AD is thick.
  • the linear expansion coefficients of the structure SP and the adhesive are different, and in the process of heating the adhesive, the structure expands while the adhesive contracts.
  • the adhesive thickness is less than 0.5 ⁇ m
  • the adhesive force between the structure SP and the reinforcing member 2 decreases due to the difference in expansion between the two, making it easy to separate them.
  • the distance between the structure and the reinforcing member is narrow, it becomes difficult for air bubbles BU trapped between the two to be discharged, which not only reduces the amount of adhesive placed between them, but also reduces the amount of adhesive placed between them.
  • the bubbles expand, causing further separation between the two.
  • the bubbles also change the characteristics of the cladding layer and increase the propagation loss of the optical waveguide.
  • the thickness of the adhesive layer exceeds 2.0 ⁇ m, the fiber and optical component LB bonded to the end of the optical waveguide element cannot absorb the shrinkage of the adhesive, and the adhesive layer A crack CR occurs at the joint with the optical component, making it easy to peel off.
  • the bonding area and the thickness of the bonding layer for bonding the structure and the reinforcing member no consideration was given to the bonding area and the thickness of the bonding layer for bonding the structure and the reinforcing member.
  • Patent Application No. 2020-165004 (filing date: September 30, 2020)
  • the problem to be solved by the present invention is to provide an optical waveguide element that can solve the above-mentioned problems and appropriately set the bonding relationship between the optical waveguide substrate and the reinforcing member.
  • Another object of the present invention is to provide an optical modulation device and an optical transmitter using the optical waveguide element.
  • an optical waveguide element of the present invention an optical modulation device using the same, and an optical transmitter have the following technical features.
  • An optical waveguide substrate including an optical waveguide, a reinforcing member disposed above the optical waveguide near the end of the optical waveguide, and an adhesive layer between the optical waveguide substrate and the reinforcing member.
  • a plurality of structures are arranged between the optical waveguide substrate and the reinforcing member so as to sandwich the optical waveguide, and the first structure is arranged between the upper surface of the structure and the reinforcing member.
  • An adhesive layer is disposed between the reinforcing member and the area of the upper surface of the reinforcing member is set to be at least a predetermined ratio to the area of the lower surface of the reinforcing member, and the second structure is It is characterized in that the thickness of the adhesive layer disposed between the body and the reinforcing member is set within a predetermined range.
  • the optical waveguide device described in (1) above is characterized in that the predetermined ratio is 50% or more.
  • the predetermined range is 0.5 ⁇ m or more and 2.0 ⁇ m or less.
  • the second structure is arranged in a stacked manner on the first structure.
  • the area of the top surface of the second structure is smaller than the area of the top surface of the first structure.
  • the optical waveguide element according to (1) above is characterized in that a spot size conversion section is formed in the optical waveguide disposed below the reinforcing member.
  • the optical waveguide element described in (1) above is an optical modulation device that is housed in a housing and includes an optical fiber that inputs or outputs a light wave to the optical waveguide.
  • the optical waveguide element is provided with a modulation electrode for modulating the light wave propagating through the optical waveguide, and the modulation signal input to the modulation electrode of the optical waveguide element is It is characterized by having an amplifying electronic circuit inside the housing.
  • An optical transmitter comprising the optical modulation device according to (8) or (9) above, and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
  • the present invention provides an optical waveguide substrate including an optical waveguide, a reinforcing member disposed above the optical waveguide near an end of the optical waveguide, and an adhesive layer between the optical waveguide substrate and the reinforcing member.
  • an optical waveguide element that is bonded using and the reinforcing member and the area of the upper surface of the reinforcing member is set to be at least a predetermined ratio to the area of the lower surface of the reinforcing member, and the second structure is Since the thickness of the adhesive layer disposed between the structure and the reinforcing member is set within a predetermined range, it is possible to appropriately set the bonding relationship between the optical waveguide substrate and the reinforcing member. Become.
  • the predetermined ratio is 50% or more, it is possible to ensure sufficient bonding strength with the adhesive layer between the first structure and the reinforcing member. Further, since the predetermined range is 0.5 ⁇ m or more and 2.0 ⁇ m or less, it is possible to appropriately set the thickness of the adhesive layer between the first structure and the reinforcing member. By using such an optical waveguide element, it is also possible to provide an optical modulation device and an optical transmitter that exhibit similar effects.
  • FIG. 2 is a plan view showing a conventional optical waveguide element.
  • FIG. 2 is a sectional view taken along the dashed line A-A' in FIG. 1;
  • FIG. 2 is a sectional view taken along the dashed line B-B' in FIG. 1;
  • FIG. 3 is a plan view showing another conventional optical waveguide element.
  • 5 is a cross-sectional view taken along the dashed line A-A' in FIG. 4.
  • FIG. 5 is a cross-sectional view taken along the dashed line B-B' in FIG. 4.
  • FIG. 3 is a plan view showing a second embodiment of the optical waveguide device according to the present invention.
  • 9 is a sectional view taken along the dashed line A-A' in FIG. 9.
  • FIG. FIG. 7 is a plan view showing a third embodiment of the optical waveguide device according to the present invention.
  • 11 is a sectional view taken along the dashed line A-A' in FIG. 11.
  • FIG. 7 is a plan view showing a fourth example of the optical waveguide substrate according to the present invention.
  • 13 is a sectional view taken along the dashed line A-A' in FIG. 13.
  • FIG. It is a top view which shows the 5th Example of the optical waveguide element based on this invention.
  • 15 is a sectional view taken along the dashed line A-A' in FIG. 15.
  • FIG. 10 is a plan view showing an example of application of the second structure shown in FIG. 9.
  • FIG. 12 is a plan view showing an example of application of the second structure shown in FIG. 11.
  • FIG. 10 is a plan view showing an example of application of the second structure shown in FIG. 9.
  • FIG. 16 is a plan view showing an application example of the second structure shown in FIG. 15.
  • FIG. 16 is a plan view showing an application example of the second structure shown in FIG. 15.
  • FIG. 16 is a plan view showing an application example of the second structure shown in FIG. 15.
  • FIG. 1 is a plan view illustrating an optical modulation device and an optical transmitter using the optical waveguide element of the present invention.
  • the optical waveguide element of the present invention includes an optical waveguide substrate 1 (11) provided with an optical waveguide 10, and an optical waveguide substrate 1 (11) disposed above the optical waveguide near the end of the optical waveguide.
  • the optical waveguide is sandwiched between the optical waveguide substrate and the reinforcing member.
  • the first structure ST1 has an adhesive layer arranged between the upper surface of the structure and the reinforcing member, and the area of the upper surface is larger than the area of the lower surface of the reinforcing member.
  • the second structure ST2 (ST20 to ST22) has a thickness of an adhesive layer disposed between the first structure and the reinforcing member set within a predetermined range. It is characterized by being configured to.
  • the vicinity of the end of the optical waveguide in the present invention refers to the range of L from the end of the optical waveguide, where L is the length of the reinforcing member in the optical waveguide extending direction, or the area near the end of the optical waveguide where the spot size is converted.
  • the part SSC refers to the range L from the end of the spot size conversion part SSC, and at least a part of the reinforcing member may be fixed to that range.
  • At least a part of the strong member is fixed in a range of 100 ⁇ m or less from the end of the optical waveguide or spot size converter SSC, more preferably in a range of 50 ⁇ m or less, More preferably, at least a portion of the reinforcing member is fixed within a range of 20 ⁇ m or less.
  • materials having an electro-optic effect include lithium niobate (LN), lithium tantalate (LT), and PLZT (lead lanthanum zirconate titanate). Substrates and vapor-grown films made of these materials can be used. Furthermore, various materials such as semiconductor materials and organic materials can also be used as optical waveguides.
  • the optical waveguide 10 can be formed by thermally diffusing Ti or the like on an LN substrate, or by etching the substrate 1 other than the optical waveguide, or by forming grooves on both sides of the optical waveguide. It is possible to use a rib-type optical waveguide with a convex portion. Furthermore, it is also possible to make the refractive index higher by diffusing Ti or the like onto the substrate surface using a thermal diffusion method, a proton exchange method, etc. in accordance with the rib-type optical waveguide. The following explanation will focus on examples using the rib-type optical waveguide 10 and the spot size converter SSC, but these ideas also apply to other optical waveguides with convex portions, such as Ti diffusion waveguides. It is. Moreover, the "optical waveguide" in the present invention is a concept that also includes a "spot size conversion section.”
  • the thickness of the substrate (thin plate) on which the optical waveguide 10 is formed is set to 10 ⁇ m or less, more preferably 5 ⁇ m or less, and even more preferably 1 ⁇ m or less in order to achieve velocity matching between the microwave and light wave of the modulation signal. Further, the height of the rib-type optical waveguide is set to 4 ⁇ m or less, more preferably 3 ⁇ m or less, and still more preferably 1 ⁇ m or less or 0.4 ⁇ m or less. It is also possible to form a vapor phase growth film on the holding substrate 11 and process the film into the shape of an optical waveguide.
  • the substrate 1 on which the optical waveguide is formed is adhesively fixed to the holding substrate 11 by direct bonding or via an adhesive layer such as resin, in order to increase mechanical strength.
  • the holding substrate 11 to be directly bonded is made of a material that has a refractive index lower than that of the optical waveguide or the substrate on which the optical waveguide is formed and has a coefficient of thermal expansion close to that of the optical waveguide, such as a substrate containing an oxide layer such as crystal, glass, or sapphire. is suitably used.
  • Other composite substrates such as SOI and LNOI, in which a silicon oxide layer is formed on a silicon substrate, and a silicon oxide layer formed on an LN substrate, can also be used.
  • the "optical waveguide substrate” in the present invention includes not only an “optical waveguide” or a "substrate on which an optical waveguide is formed” but also the "holding substrate”.
  • a spot size converter SSC is formed as shown in FIGS. 9 and 10.
  • the spot size converter applied to the optical waveguide device of the present invention is not limited to these, but is a so-called tapered spot size converter in which the width and height of the optical waveguide gradually increases toward the edge of the substrate. It may be.
  • the spot size conversion unit SSC has a configuration in which the tip of the rib-shaped optical waveguide 10 has a tapered shape with a narrower width, and a block portion 100 serving as a core portion is arranged to surround it.
  • the distance h between the top surface of the spot size converter SSC and the reinforcing member (upper substrate) 2 shown in FIG. 10 is set to 0.2 to 1.5 times the mode field diameter of the spot size converter SSC. ing.
  • the reinforcing member 2 is arranged above the optical waveguide (rib type optical waveguide 10) or the spot size converter SSC.
  • the reinforcing member 2 a material having the same refractive index and linear expansion coefficient as the holding substrate 11 is used. If the linear expansion coefficients match, it becomes possible to reduce defects such as the reinforcing member (upper substrate) coming off due to thermal stress, and an optical waveguide element with excellent heat resistance can be obtained.
  • the adhesive (adhesive layer) 3 for bonding the reinforcing member 2 and the optical waveguide substrate 1 or the holding substrate 11 may be an adhesive made of a UV curing resin, an acrylic resin, an epoxy resin, or the like.
  • the optical waveguide device of the present invention is characterized by the first structure ST1 that maintains the bonding strength between the optical waveguide substrate 1 (11) and the reinforcing member 2, and the thickness of the adhesive layer between the optical waveguide substrate and the reinforcing member. and a second structure ST2 (ST20 to ST22) for appropriately setting the height.
  • the second structure ST2 is formed on the top of the first structure ST1, and the top surface of the second structure ST2 is formed at a higher position than the top surface of the first structure ST1. There is.
  • the first structure ST1 is arranged to sandwich the optical waveguide, and similarly to Patent Document 1, it functions as a structure for protecting the optical waveguide including the spot size converter SSC.
  • the first structure ST1 needs to ensure stable bonding strength by the adhesive layer disposed between the first structure and the reinforcing member 2. Therefore, as shown in FIGS. 7 and 9, the ratio of the total area (S1+S2) of the top surface of the first structure ST1 to the area S0 of the bottom surface of the reinforcing member 2 is 50% or more. preferable.
  • the area of the top surface of the first structure as shown in FIGS. 7 to 10 it is possible to exclude the area of the portion where the second structure ST2 is arranged on the top surface of the first structure ST1. preferable.
  • the height of the block section 100 of the spot size conversion section SSC is approximately the same as the height of the first structure, it is possible to add it to the total area of the upper surface of the first structure.
  • the function of protecting the optical waveguide can be achieved by making the first structure ST1 higher than the height of the optical waveguide 10.
  • air bubbles are likely to enter between the optical waveguide and the first structure or between the first structures.
  • the second structures ST2 are also arranged to sandwich the optical waveguide, and it is better to ensure as wide a gap as possible between the second structures sandwiching the optical waveguide between the optical waveguide substrate 1 (11) and the reinforcing member 2. This is preferable in order to maintain a uniform distance between the two.
  • the second structure ST2 plays a role exclusively in maintaining the distance H between the first structure ST1 and the reinforcing member 2 within a predetermined range. Specifically, the predetermined range is 0.5 ⁇ m or more and 2.0 ⁇ m or less.
  • the distance h between the optical waveguide 10 (spot size converter SSC) and the reinforcing member 2 is set to 0.2 to 1.5 times the MFD of the optical waveguide, etc., in order to suppress the loss of propagating light due to the reinforcing member. It is preferable to set it within a range.
  • the thickness of the second structure ST2 is less than 0.5 ⁇ m even if the upper end of the second structure contacts the reinforcing member 2 or an adhesive is interposed between the upper end and the reinforcing member 2. Set. For this reason, it is preferable to set the area of the upper surface of the second structure to be as small as possible.
  • the number of second structures ST2 is not limited to two as shown in FIGS. 7 to 10, and more may be arranged as described later. When the width of the second structure is large or the number of the second structures is large, the mechanical strength of the second structure is also high, so a member that protects the optical waveguide (spot size converter SSC) as shown in FIG. 10 is used. Also, reliability can be further improved as a member that maintains the distance H between the first structure ST1 and the reinforcing member 2 within a predetermined range.
  • FIGS. 7 to 10 show the arrangement in which the second structure ST2 is stacked on top of the first structure ST1
  • the present invention is not limited to this, and as shown in FIGS. 11 to 16, It is also possible to arrange a second structure separately from the first structure.
  • the second structure When the second structure is placed separately from the first structure, the second structure is placed outside the first structure, and the distance between the second structures is as small as possible. It is preferable to secure as much space as possible.
  • the first structure may be placed not only on both sides of the optical waveguide, but also on only one side.
  • the first structure may be arranged outside the second structure (on the opposite side to the optical waveguide). Also good.
  • resin materials such as photoresists (permanent resists) are suitable for various shapes and arrangements, and can be suitably used.
  • materials used in the manufacturing process of the optical waveguide device such as a part of the optical waveguide substrate 1, a conductive material such as gold used in the electrodes, a block part of the spot size converter SSC, and other parts of the optical waveguide. It is also possible to use a combination of resin materials constituting the protective film.
  • resin used for the permanent resist various materials such as polyamide resin, melamine resin, phenol resin, amino resin, and epoxy resin can be used.
  • the same conductive material as the electrode is used for the first structure ST1
  • the same conductive material as the electrode is used for the second structure ST2.
  • a configuration using a resin material, or a configuration using a resin material such as a photoresist (permanent resist) or the same conductive material as the electrodes for both the first structure ST1 and the second structure ST2 can be adopted.
  • the same material as the optical waveguide substrate 1 may be used as the material other than the above, or quartz or other glass materials may be used and formed by various processes such as sputtering or vapor deposition.
  • the first structure ST1 and the second structure are configured separately, and the first structure is made of the same material as the protective film (permanent resist) that covers the optical waveguide. Alternatively, it can be formed of the same material as the block section 100 of the spot size conversion section SSC. Further, the second structure has a laminated structure in which a portion ST21 made of the same material as the electrode material and a portion ST20 made of a photoresist material.
  • the second structure has a structure in which a portion ST20 made of a photoresist material is laminated on a portion ST22 of the optical waveguide substrate 1. Furthermore, in FIGS. 15 and 16, the second structure has a portion ST21 made of an electrode material laminated on a portion ST22 of the optical waveguide substrate 1, and a portion ST20 made of a photoresist material is further laminated. are doing.
  • the second structures ST2 and ST20 are formed separately on one side of the structure ST1, not on the top of the first structure ST1, and the second structures ST2 and ST20 are formed separately on one side of the structure ST1.
  • the upper surface is formed to be higher than the upper surface of the first structure ST1. Note that the heights of the portion ST21 made of the same material as the electrode material in FIGS. 11 and 12 and the portion ST22 of the optical waveguide substrate 1 in FIGS. 13 and 14 are the same as those of the optical waveguide 10 of the spot size converter SSC.
  • the block part 100 of the spot size conversion part SSC, the first structure ST1, and the part ST20 made of the photoresist material which is the second structure are made of the same material, and each is processed in the same process. may be formed at the same height. As a result, the manufacturing process can be significantly reduced, and variations in the height of each structure can be suppressed.
  • FIG. 17 is a diagram illustrating variations in the arrangement of the second structure ST2 placed on the first structure ST1.
  • FIG. 18 is a diagram illustrating variations in the arrangement of the second structures (ST20 and ST21) that are arranged separately from the first structure ST1. In both figures, only the portion located at the lower part of the reinforcing member is extracted and illustrated. As shown in FIGS. 17A and 18A, it is possible to form a second structure that extends long along the direction in which the optical waveguide extends. As the length increases, the mechanical strength of the second structure increases, but bubbles remain because the bubbles can only escape from the adhesive layer in the area sandwiched between the two second structures in the vertical direction of the drawing. More likely.
  • the reinforcing members can be arranged while ensuring a route for air bubbles to be discharged. Stability (wobble prevention) is also increased.
  • the length of the second structure is shortened, and the length of the second structure is not only removed, but also placed between the second structure and the reinforcing member. It is also possible to reduce the amount of adhesive layer used and to prevent air bubbles from remaining.
  • these structures appear to be extremely unstable because the reinforcing member is supported only by the two second structures, this can be resolved by devising the manufacturing process.
  • the spot size converters SSC of a pair of optical waveguide substrates are arranged so as to face each other, so that a total of four spot size converters SSC formed on the two spot size converters SSC are A reinforcing member is fixed on top of the second structure. Thereby, the reinforcing member is stably fixed to the second structure.
  • a pair of optical waveguide substrates can be obtained by cutting the centers of the two spot size converters SSC.
  • FIG. 20 An example is shown in which the number of second structures is set to three in FIG. 20, four in FIG. 21, and eight in FIG. 22.
  • the placement of the reinforcing member is stabilized by securing three points on the plane that supports the reinforcing member, so if the area of the top surface of the second structure is small, it is recommended to arrange three or more reinforcing members. is preferred.
  • the optical waveguide element of the present invention is provided with a modulation electrode that modulates the light wave propagating through the optical waveguide 10 on the optical waveguide substrate 1 (11), and is housed in a housing CA as shown in FIG. 23. Furthermore, by providing an optical fiber (F) for inputting and outputting light waves to the optical waveguide, the optical modulation device MD can be configured.
  • the optical fiber is introduced into the housing through a through hole penetrating the side wall of the housing, and is directly joined to the optical waveguide element.
  • the optical waveguide element and the optical fiber can also be optically connected via a spatial optical system.
  • the optical transmitter OTA can be configured by connecting to the optical modulating device MD an electronic circuit (digital signal processor DSP) that outputs a modulation signal S0 that causes the optical modulating device MD to perform a modulation operation. Since the modulation signal S applied to the optical waveguide element needs to be amplified, a driver circuit DRV is used.
  • the driver circuit DRV and the digital signal processor DSP can be placed outside the case CA, but they can also be placed inside the case CA. In particular, by arranging the driver circuit DRV within the housing, it becomes possible to further reduce the propagation loss of the modulated signal from the driver circuit.
  • an optical waveguide element in which the bonding relationship between the optical waveguide substrate and the reinforcing member can be appropriately set. Furthermore, it is possible to provide an optical modulation device and an optical transmitter using the optical waveguide element.

Abstract

The purpose of the present invention is to provide an optical waveguide element where a joining relationship between an optical waveguide substrate and a reinforcing member can be set appropriately.　The present invention is an optical waveguide element provided with an optical waveguide substrate 1 (11) which is provided with an optical waveguide 10, and a reinforcing member 2 which is disposed above the optical waveguide near an end section of the optical waveguide, the optical waveguide substrate and the reinforcing member being joined by an adhesive layer AD interposed therebetween, wherein: a plurality of structures are disposed between the optical waveguide substrate and the reinforcing member so as to sandwich the optical waveguide; a first structure ST1 is configured such that the adhesive layer is disposed between a top surface of the structure and the reinforcing member, and is set such that the area of the top surface is at least a prescribed percentage of the area of the bottom surface of the reinforcing member; and a second structure ST2 is configured such that the thickness of the adhesive layer disposed between the first structure and the reinforcing member is set to a prescribed range.

Description

光導波路素子及びそれを用いた光変調デバイス並びに光送信装置Optical waveguide element, optical modulation device and optical transmitter using the same
　本発明は、光導波路素子及びそれを用いた光変調デバイス並びに光送信装置に関し、特に、光導波路を備えた光導波路基板と、該光導波路の端部付近で、該光導波路の上側に配置される補強部材と、該光導波路基板と該補強部材とは接着層を介して接合される光導波路素子に関する。 The present invention relates to an optical waveguide element, an optical modulation device using the same, and an optical transmitter, and particularly relates to an optical waveguide substrate including an optical waveguide, and an optical waveguide substrate disposed above the optical waveguide near the end of the optical waveguide. The present invention relates to a reinforcing member, and an optical waveguide element in which the optical waveguide substrate and the reinforcing member are bonded via an adhesive layer.
　光計測技術分野や光通信技術分野において、光変調器など、光導波路を形成した基板を用いた光導波路素子が多用されている。例えば、ニオブ酸リチウム（ＬＮ）のような電気光学効果を有する基板などにＴｉなどの高屈折率材料を熱拡散する方法やリブ型構造（凸状部）を形成する方法で光導波路が形成される。光導波路を形成した光導波路基板に対しては、外部から入力光を導入又は外部に出力光を導出することが行われる。基板上の光導波路に外部からの入力光を導入するためには、光導波路の入力部が形成され基板の端面には、光ファイバーやレンズなどの光学ブロックが接続される。また、光導波路の出力部が形成された基板の端面にも、出力光を適正に導出するため、光ファイバー、レンズ、偏波合成手段、反射手段などの光学ブロックが接続される。 In the optical measurement technology field and the optical communication technology field, optical waveguide elements such as optical modulators that use a substrate on which an optical waveguide is formed are often used. For example, optical waveguides are formed by thermally diffusing a high refractive index material such as Ti on a substrate with an electro-optic effect such as lithium niobate (LN), or by forming a rib-type structure (convex portion). Ru. Input light is introduced from the outside or output light is led out to the optical waveguide substrate on which the optical waveguide is formed. In order to introduce input light from the outside into the optical waveguide on the substrate, an input section of the optical waveguide is formed, and an optical block such as an optical fiber or a lens is connected to the end surface of the substrate. In addition, optical blocks such as optical fibers, lenses, polarization combining means, reflecting means, etc. are connected to the end face of the substrate on which the output portion of the optical waveguide is formed, in order to properly guide the output light.
　光導波路基板への光学ブロックの接続に際しては、光学ブロックをより強固に固定するため、光導波路基板の端面に沿って当該基板上に補強部材を接着剤（接着層）で固定している。これにより光学ブロックは、光導波路基板と補強部材の２つの端面に接合されることとなる。 When connecting the optical block to the optical waveguide substrate, in order to more firmly fix the optical block, a reinforcing member is fixed onto the substrate along the end surface of the optical waveguide substrate with an adhesive (adhesive layer). As a result, the optical block is joined to the two end faces of the optical waveguide substrate and the reinforcing member.
　他方、近年の通信量の増大に伴い、光変調器において、高速化並びに設置スペースの制限による小型化が望まれている。このため、光変調器に組み込む光導波路素子の光導波路を、リブ型構造で形成し、光波のモールドフィールド径（ＭＦＤ）を１μｍ程度まで小径化する必要がある。小径化により光の閉じ込めが強くなることから、導波路の曲げ半径を小さくすることができ、光導波路素子並びに光変調器を小型化することができる。 On the other hand, with the increase in communication traffic in recent years, optical modulators are desired to be faster and smaller due to limitations in installation space. Therefore, it is necessary to form the optical waveguide of the optical waveguide element incorporated into the optical modulator with a rib-type structure and reduce the mold field diameter (MFD) of the light wave to about 1 μm. Since light confinement is strengthened by reducing the diameter, the bending radius of the waveguide can be reduced, and the optical waveguide element and optical modulator can be downsized.
　しかしながら、光導波路素子の光導波路端面に接合する光ファイバー等の光学部品はＭＦＤが１０μｍ程度であり、光導波路のＭＦＤ（例えば３μｍ以下）とは大きく異なる。このため、光結合損失を抑えるよう、光導波路素子の端部には、スポットサイズ変換部を配置し、ＭＦＤを大径化させている。スポットサイズ変換部を用いる場合でも、光導波路素子の端部に接合する光ファイバー等の光学部品との接合強度を上げるため、光導波路基板の端面に沿って補強部材（上部基板）を配置している。 However, the MFD of optical components such as optical fibers bonded to the optical waveguide end face of the optical waveguide element is approximately 10 μm, which is significantly different from the MFD of the optical waveguide (for example, 3 μm or less). Therefore, in order to suppress optical coupling loss, a spot size converter is disposed at the end of the optical waveguide element to increase the diameter of the MFD. Even when using a spot size converter, a reinforcing member (upper substrate) is placed along the end surface of the optical waveguide substrate in order to increase the bonding strength with optical components such as optical fibers that are bonded to the end of the optical waveguide element. .
　また、補強部材と光導波路基板とを接合する接着剤として、スポットサイズ変換部を構成する材料の屈折率よりも低い屈折率の材料を選択することで、スポットサイズ変換部の周囲に配置される接着層が、スポットサイズ変換部のクラッド層として機能する。 In addition, by selecting a material with a refractive index lower than that of the material constituting the spot size converting section as the adhesive for bonding the reinforcing member and the optical waveguide substrate, it is possible to arrange the spot size converting section around the spot size converting section. The adhesive layer functions as a cladding layer of the spot size conversion section.
　リブ型構造の光導波路（以下ではリブ型光導波路ともいう）やスポットサイズ変換器が配置された部分で補強部材を配置する場合、リブ型構造の光導波路が光導波路基板から突出しているため、光導波路基板に対して補強部材を平行に貼り合わせることが困難となる。また、補強部材が傾くことで、光導波路などを破損したり、スポットサイズ変換器のクラッド層が傾くことでＭＦＤにバラツキが生じる。 When placing a reinforcing member in a part where an optical waveguide with a rib-type structure (hereinafter also referred to as a rib-type optical waveguide) or a spot size converter is arranged, since the optical waveguide with a rib-type structure protrudes from the optical waveguide substrate, It becomes difficult to attach the reinforcing member parallel to the optical waveguide substrate. Furthermore, the reinforcing member may be tilted, which may damage the optical waveguide, and the cladding layer of the spot size converter may be tilted, causing variations in the MFD.
　特許文献１においては、スポットサイズ変換部を挟むように、スポットサイズ変換部よりも高いレジスト等の樹脂構造体を配置し、スポットサイズ変換部などの破損やＭＦＤのばらつきの発生を抑えることが提案されている。また、該構造体の上面に溝を施すことで、余分な接着剤を排出することも開示されている。 Patent Document 1 proposes that a resin structure such as a resist that is higher than the spot size converter is placed so as to sandwich the spot size converter to suppress damage to the spot size converter and variations in the MFD. has been done. It is also disclosed that grooves are formed on the top surface of the structure to drain excess adhesive.
　特許文献１のような従来構成においては、光導波路基板側に配置された部材で、補強部材との接合面積が最も大きい部材は当該構造体が占めており、具体的には、補強部材の接着面の面積の約５０％以上を占めている。図１乃至６は光導波路基板（１１）と補強部材２との接合状態を示した図である。図１の一点鎖線Ａ－Ａ’における断面図を図２に示し、図１の一点鎖線Ｂ－Ｂ’における断面図を図３に示している。同様に図４の一点鎖線Ａ－Ａ’における断面図を図５に示し、図４の一点鎖線Ｂ－Ｂ’における断面図を図６に示している。図１及び図４で太い点線枠２は補強部材を配置する位置を示している。 In the conventional configuration as in Patent Document 1, among the members arranged on the optical waveguide substrate side, the member having the largest bonding area with the reinforcing member is occupied by the structure, and specifically, the bonding of the reinforcing member It occupies about 50% or more of the surface area. 1 to 6 are diagrams showing the bonded state of the optical waveguide substrate (11) and the reinforcing member 2. FIG. FIG. 2 shows a cross-sectional view taken along the dashed-dotted line A-A' in FIG. 1, and FIG. 3 shows a cross-sectional view taken along the dashed-dotted line B-B' in FIG. Similarly, FIG. 5 shows a cross-sectional view taken along the dashed-dotted line A-A' in FIG. 4, and FIG. 6 shows a cross-sectional view taken along the dashed-dotted line B-B' in FIG. In FIGS. 1 and 4, the thick dotted line frame 2 indicates the position where the reinforcing member is placed.
　図１乃至３は接着層ＡＤの厚みが薄い場合を示し、図４乃至６は接着層ＡＤの厚みが厚い場合を示している。一般に、構造体ＳＰと接着剤の線膨張係数は異なり、接着剤が加熱される過程では、構造体が膨張するのに対し接着剤は収縮する。例えば、接着厚さが０．５μｍ未満の場合、両者の膨張差のため、構造体ＳＰと補強部材２との接着力が低下し剥離し易くなる。しかも、構造体と補強部材との間隔が狭いため、両者の間に捕捉された気泡ＢＵが排出され難くなり、両者の間に配置される接着剤の量が減少するだけでなく、加熱過程で気泡が膨張し、両者の剥離がより一層発生する。また、気泡によりクラッド層の特性も変化し、光導波路の伝搬損失も増加する。 1 to 3 show the case where the adhesive layer AD is thin, and FIGS. 4 to 6 show the case where the adhesive layer AD is thick. Generally, the linear expansion coefficients of the structure SP and the adhesive are different, and in the process of heating the adhesive, the structure expands while the adhesive contracts. For example, when the adhesive thickness is less than 0.5 μm, the adhesive force between the structure SP and the reinforcing member 2 decreases due to the difference in expansion between the two, making it easy to separate them. Moreover, since the distance between the structure and the reinforcing member is narrow, it becomes difficult for air bubbles BU trapped between the two to be discharged, which not only reduces the amount of adhesive placed between them, but also reduces the amount of adhesive placed between them. The bubbles expand, causing further separation between the two. In addition, the bubbles also change the characteristics of the cladding layer and increase the propagation loss of the optical waveguide.
　一方、接着層の厚さが２．０μｍを越える場合、図６に示すように、光導波路素子の端部に接合したファイバーや光学部品ＬＢが、接着剤の収縮を吸収できず、接着層と光学部品との接合部に亀裂ＣＲが発生し、剥離し易くなる。
　このように、従来は、構造体と補強部材との接合に係る接着面積や接着層の厚さについては、全く考慮されていなかった。 On the other hand, when the thickness of the adhesive layer exceeds 2.0 μm, the fiber and optical component LB bonded to the end of the optical waveguide element cannot absorb the shrinkage of the adhesive, and the adhesive layer A crack CR occurs at the joint with the optical component, making it easy to peel off.
As described above, in the past, no consideration was given to the bonding area and the thickness of the bonding layer for bonding the structure and the reinforcing member.
特願２０２０－１６５００４号（出願日２０２０年９月３０日）Patent Application No. 2020-165004 (filing date: September 30, 2020)
　本発明が解決しようとする課題は、上述したような問題を解決し、光導波路基板と補強部材との接合関係を適正に設定することが可能な光導波路素子を提供することである。また、その光導波路素子を用いた光変調デバイスと光送信装置を提供することである。 The problem to be solved by the present invention is to provide an optical waveguide element that can solve the above-mentioned problems and appropriately set the bonding relationship between the optical waveguide substrate and the reinforcing member. Another object of the present invention is to provide an optical modulation device and an optical transmitter using the optical waveguide element.
　上記課題を解決するため、本発明の光導波路素子及びそれを用いた光変調デバイス並びに光送信装置は、以下の技術的特徴を有する。
（１）　光導波路を備えた光導波路基板と、該光導波路の端部付近で、該光導波路の上側に配置される補強部材と、該光導波路基板と該補強部材とは接着層を介して接合される光導波路素子において、該光導波路基板と該補強部材との間には、該光導波路を挟むように複数の構造体が配置され、第１の構造体は、該構造体の上面と該補強部材との間に接着層を配置し、該補強部材の下面の面積に対して該上面の面積が所定割合以上となるように設定され、第２の構造体は、前記第１の構造体と該補強部材との間に配置される接着層の厚みを所定の範囲に設定するよう構成されていることを特徴とする。 In order to solve the above problems, an optical waveguide element of the present invention, an optical modulation device using the same, and an optical transmitter have the following technical features.
(1) An optical waveguide substrate including an optical waveguide, a reinforcing member disposed above the optical waveguide near the end of the optical waveguide, and an adhesive layer between the optical waveguide substrate and the reinforcing member. In the optical waveguide element to be bonded, a plurality of structures are arranged between the optical waveguide substrate and the reinforcing member so as to sandwich the optical waveguide, and the first structure is arranged between the upper surface of the structure and the reinforcing member. An adhesive layer is disposed between the reinforcing member and the area of the upper surface of the reinforcing member is set to be at least a predetermined ratio to the area of the lower surface of the reinforcing member, and the second structure is It is characterized in that the thickness of the adhesive layer disposed between the body and the reinforcing member is set within a predetermined range.
（２）　上記（１）に記載の光導波路素子において、前記所定割合は５０％以上であることを特徴とする。 (2) The optical waveguide device described in (1) above is characterized in that the predetermined ratio is 50% or more.
（３）　上記（１）又は（２）に記載の光導波路素子において、前記所定の範囲は０．５μｍ以上、２．０μｍ以下であることを特徴とする。 (3) In the optical waveguide device according to (1) or (2) above, the predetermined range is 0.5 μm or more and 2.0 μm or less.
（４）　上記（１）に記載の光導波路素子において、前記第２の構造体は、前記第１の構造体の上に積層して配置されていることを特徴とする。 (4) In the optical waveguide device according to (1) above, the second structure is arranged in a stacked manner on the first structure.
（５）　上記（１）に記載の光導波路素子において、該光導波路と前記第２の構造体との間に、前記第１の構造体の少なくとも一部が配置されていることを特徴とする。 (5) The optical waveguide element according to (1) above, characterized in that at least a part of the first structure is disposed between the optical waveguide and the second structure. .
（６）　上記（１）に記載の光導波路素子において、前記第２の構造体の上面の面積は、前記第１の構造体の上面の面積よりも小さいことを特徴とする。 (6) In the optical waveguide device according to (1) above, the area of the top surface of the second structure is smaller than the area of the top surface of the first structure.
（７）　上記（１）に記載の光導波路素子において、該補強部材の下側に配置される該光導波路には、スポットサイズ変換部が形成されていることを特徴とする。 (7) The optical waveguide element according to (1) above is characterized in that a spot size conversion section is formed in the optical waveguide disposed below the reinforcing member.
（８）　上記（１）に記載の光導波路素子は、筐体内に収容され、該光導波路に光波を入力又は出力する光ファイバーを備えることを特徴とする光変調デバイスである。 (8) The optical waveguide element described in (1) above is an optical modulation device that is housed in a housing and includes an optical fiber that inputs or outputs a light wave to the optical waveguide.
（９）　上記（８）に記載の光変調デバイスにおいて、該光導波路素子は該光導波路を伝搬する光波を変調するための変調電極を備え、該光導波路素子の変調電極に入力する変調信号を増幅する電子回路を該筐体の内部に有することを特徴とする。 (9) In the optical modulation device according to (8) above, the optical waveguide element is provided with a modulation electrode for modulating the light wave propagating through the optical waveguide, and the modulation signal input to the modulation electrode of the optical waveguide element is It is characterized by having an amplifying electronic circuit inside the housing.
（１０）　上記（８）又は（９）に記載の光変調デバイスと、該光変調デバイスに変調動作を行わせる変調信号を出力する電子回路とを有することを特徴とする光送信装置である。 (10) An optical transmitter comprising the optical modulation device according to (8) or (9) above, and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
　本発明は、光導波路を備えた光導波路基板と、該光導波路の端部付近で、該光導波路の上側に配置される補強部材と、該光導波路基板と該補強部材とは接着層を介して接合される光導波路素子において、該光導波路基板と該補強部材との間には、該光導波路を挟むように複数の構造体が配置され、第１の構造体は、該構造体の上面と該補強部材との間に接着層を配置し、該補強部材の下面の面積に対して該上面の面積が所定割合以上となるように設定され、第２の構造体は、前記第１の構造体と該補強部材との間に配置される接着層の厚みを所定の範囲に設定するよう構成されているため、光導波路基板と補強部材との接合関係を適正に設定することが可能となる。 The present invention provides an optical waveguide substrate including an optical waveguide, a reinforcing member disposed above the optical waveguide near an end of the optical waveguide, and an adhesive layer between the optical waveguide substrate and the reinforcing member. In an optical waveguide element that is bonded using and the reinforcing member, and the area of the upper surface of the reinforcing member is set to be at least a predetermined ratio to the area of the lower surface of the reinforcing member, and the second structure is Since the thickness of the adhesive layer disposed between the structure and the reinforcing member is set within a predetermined range, it is possible to appropriately set the bonding relationship between the optical waveguide substrate and the reinforcing member. Become.
　さらに、前記所定割合は５０％以上であるため、第１の構造体と補強部材との間の接着層と十分な接合強度を確保できる。また、前記所定の範囲は０．５μｍ以上、２．０μｍ以下であるため、第１の構造体と補強部材との間の接着層の厚さを適正に設定すること可能となる。
　このような光導波路素子を用いることで、同様の効果を奏する光変調デバイスと光送信装置を提供することも可能となる。 Furthermore, since the predetermined ratio is 50% or more, it is possible to ensure sufficient bonding strength with the adhesive layer between the first structure and the reinforcing member. Further, since the predetermined range is 0.5 μm or more and 2.0 μm or less, it is possible to appropriately set the thickness of the adhesive layer between the first structure and the reinforcing member.
By using such an optical waveguide element, it is also possible to provide an optical modulation device and an optical transmitter that exhibit similar effects.
従来の光導波路素子を示す平面図である。FIG. 2 is a plan view showing a conventional optical waveguide element. 図１の一点鎖線Ａ－Ａ’における断面図である。FIG. 2 is a sectional view taken along the dashed line A-A' in FIG. 1; 図１の一点鎖線Ｂ－Ｂ’における断面図である。FIG. 2 is a sectional view taken along the dashed line B-B' in FIG. 1; 従来の他の光導波路素子を示す平面図である。FIG. 3 is a plan view showing another conventional optical waveguide element. 図４の一点鎖線Ａ－Ａ’における断面図である。5 is a cross-sectional view taken along the dashed line A-A' in FIG. 4. FIG. 図４の一点鎖線Ｂ－Ｂ’における断面図である。5 is a cross-sectional view taken along the dashed line B-B' in FIG. 4. FIG. 本発明に係る光導波路素子の第１の実施例を示す平面図である。1 is a plan view showing a first example of an optical waveguide device according to the present invention. 図７の一点鎖線Ａ－Ａ’における断面図である。8 is a cross-sectional view taken along the dashed line A-A' in FIG. 7. FIG. 本発明に係る光導波路素子の第２の実施例を示す平面図である。FIG. 3 is a plan view showing a second embodiment of the optical waveguide device according to the present invention. 図９の一点鎖線Ａ－Ａ’における断面図である。9 is a sectional view taken along the dashed line A-A' in FIG. 9. FIG. 本発明に係る光導波路素子の第３の実施例を示す平面図である。FIG. 7 is a plan view showing a third embodiment of the optical waveguide device according to the present invention. 図１１の一点鎖線Ａ－Ａ’における断面図である。11 is a sectional view taken along the dashed line A-A' in FIG. 11. FIG. 本発明に係る光導波路基板の第４の実施例を示す平面図である。FIG. 7 is a plan view showing a fourth example of the optical waveguide substrate according to the present invention. 図１３の一点鎖線Ａ－Ａ’における断面図である。13 is a sectional view taken along the dashed line A-A' in FIG. 13. FIG. 本発明に係る光導波路素子の第５の実施例を示す平面図である。It is a top view which shows the 5th Example of the optical waveguide element based on this invention. 図１５の一点鎖線Ａ－Ａ’における断面図である。15 is a sectional view taken along the dashed line A-A' in FIG. 15. FIG. 図９の第２の構造体の応用例を示す平面図である。10 is a plan view showing an example of application of the second structure shown in FIG. 9. FIG. 図１１の第２の構造体の応用例を示す平面図である。12 is a plan view showing an example of application of the second structure shown in FIG. 11. FIG. 図９の第２の構造体の応用例を示す平面図である。10 is a plan view showing an example of application of the second structure shown in FIG. 9. FIG. 図１５の第２の構造体の応用例を示す平面図である。16 is a plan view showing an application example of the second structure shown in FIG. 15. FIG. 図１５の第２の構造体の応用例を示す平面図である。16 is a plan view showing an application example of the second structure shown in FIG. 15. FIG. 図１５の第２の構造体の応用例を示す平面図である。16 is a plan view showing an application example of the second structure shown in FIG. 15. FIG. 本発明の光導波路素子を使用した光変調デバイス及び光送信装置を説明する平面図である。1 is a plan view illustrating an optical modulation device and an optical transmitter using the optical waveguide element of the present invention.
　以下、本発明の光導波路素子について、好適例を用いて詳細に説明する。
　本発明の光導波路素子は、図７乃至２２に示すように、光導波路１０を備えた光導波路基板１（１１）と、該光導波路の端部付近で、該光導波路の上側に配置される補強部材２と、該光導波路基板と該補強部材とは接着層ＡＤを介して接合される光導波路素子において、該光導波路基板と該補強部材との間には、該光導波路を挟むように複数の構造体が配置され、第１の構造体ＳＴ１は、該構造体の上面と該補強部材との間に接着層を配置し、該補強部材の下面の面積に対して該上面の面積が所定割合以上となるように設定され、第２の構造体ＳＴ２（ＳT２０～２２）は、前記第１の構造体と該補強部材との間に配置される接着層の厚みを所定の範囲に設定するよう構成されていることを特徴とする。 Hereinafter, the optical waveguide device of the present invention will be described in detail using preferred examples.
As shown in FIGS. 7 to 22, the optical waveguide element of the present invention includes an optical waveguide substrate 1 (11) provided with an optical waveguide 10, and an optical waveguide substrate 1 (11) disposed above the optical waveguide near the end of the optical waveguide. In an optical waveguide element in which the reinforcing member 2, the optical waveguide substrate, and the reinforcing member are bonded via the adhesive layer AD, the optical waveguide is sandwiched between the optical waveguide substrate and the reinforcing member. A plurality of structures are arranged, and the first structure ST1 has an adhesive layer arranged between the upper surface of the structure and the reinforcing member, and the area of the upper surface is larger than the area of the lower surface of the reinforcing member. The second structure ST2 (ST20 to ST22) has a thickness of an adhesive layer disposed between the first structure and the reinforcing member set within a predetermined range. It is characterized by being configured to.
　なお、本発明における光導波路の端部付近とは、補強部材の光導波路延伸方向の長さをＬとした場合、光導波路の端部からＬの範囲、または光導波路の端部にスポットサイズ変換部ＳＳＣを形成した場合はスポットサイズ変換部ＳＳＣの端部からＬの範囲を指し、それらの範囲に補強部材の少なくとも一部が固定されていればよい。
　また、光学ブロックなどの剥離を考慮すると光導波路やスポットサイズ変換部ＳＳＣの端部から１００μｍ以下の範囲に強部材の少なくとも一部が固定されていることが好ましく、より好ましくは５０μｍ以下の範囲、更に好ましくは２０μｍ以下の範囲に補強部材の少なくとも一部が固定されているとよい。 In addition, the vicinity of the end of the optical waveguide in the present invention refers to the range of L from the end of the optical waveguide, where L is the length of the reinforcing member in the optical waveguide extending direction, or the area near the end of the optical waveguide where the spot size is converted. When the part SSC is formed, it refers to the range L from the end of the spot size conversion part SSC, and at least a part of the reinforcing member may be fixed to that range.
Furthermore, in consideration of peeling off of the optical block, etc., it is preferable that at least a part of the strong member is fixed in a range of 100 μm or less from the end of the optical waveguide or spot size converter SSC, more preferably in a range of 50 μm or less, More preferably, at least a portion of the reinforcing member is fixed within a range of 20 μm or less.
　本発明の光導波路素子に使用される光導波路基板１としては、電気光学効果を有する材料は、ニオブ酸リチウム（ＬＮ）やタンタル酸リチウム（ＬＴ）、ＰＬＺＴ（ジルコン酸チタン酸鉛ランタン）などの基板や、これらの材料による気相成長膜などが利用可能である。
　また、半導体材料や有機材料など種々の材料も光導波路として利用可能である。 For the optical waveguide substrate 1 used in the optical waveguide element of the present invention, materials having an electro-optic effect include lithium niobate (LN), lithium tantalate (LT), and PLZT (lead lanthanum zirconate titanate). Substrates and vapor-grown films made of these materials can be used.
Furthermore, various materials such as semiconductor materials and organic materials can also be used as optical waveguides.
　光導波路１０としては、ＬＮ基板にＴｉ等を熱拡散して形成する光導波路や、光導波路以外の基板１をエッチングしたり、光導波路の両側に溝を形成するなど、基板の光導波路に対応する部分を凸状としたリブ型の光導波路を利用することが可能である。さらに、リブ型の光導波路に合わせて、Ｔｉなどを熱拡散法やプロトン交換法などで基板表面に拡散させることにより、屈折率をより高くすることも可能である。以下の説明は、リブ型光導波路１０やスポットサイズ変換部ＳＳＣを用いた例を中心に説明するが、これらの考え方はＴｉ拡散導波路など凸状部分を有する他の光導波路にも該当するものである。
　また、本発明における「光導波路」とは、「スポットサイズ変換部」も含む概念である。 The optical waveguide 10 can be formed by thermally diffusing Ti or the like on an LN substrate, or by etching the substrate 1 other than the optical waveguide, or by forming grooves on both sides of the optical waveguide. It is possible to use a rib-type optical waveguide with a convex portion. Furthermore, it is also possible to make the refractive index higher by diffusing Ti or the like onto the substrate surface using a thermal diffusion method, a proton exchange method, etc. in accordance with the rib-type optical waveguide. The following explanation will focus on examples using the rib-type optical waveguide 10 and the spot size converter SSC, but these ideas also apply to other optical waveguides with convex portions, such as Ti diffusion waveguides. It is.
Moreover, the "optical waveguide" in the present invention is a concept that also includes a "spot size conversion section."
　光導波路１０を形成した基板（薄板）の厚さは、変調信号のマイクロ波と光波との速度整合を図るため、１０μｍ以下、より好ましくは５μｍ以下、さらに好ましくは１μｍ以下に設定される。また、リブ型光導波路の高さは、４μｍ以下、より好ましくは３μｍ以下、さらに好ましくは１μｍ以下又は０．４μｍ以下に設定される。また、保持基板１１の上に気相成長膜を形成し、当該膜を光導波路の形状に加工することも可能である。 The thickness of the substrate (thin plate) on which the optical waveguide 10 is formed is set to 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less in order to achieve velocity matching between the microwave and light wave of the modulation signal. Further, the height of the rib-type optical waveguide is set to 4 μm or less, more preferably 3 μm or less, and still more preferably 1 μm or less or 0.4 μm or less. It is also possible to form a vapor phase growth film on the holding substrate 11 and process the film into the shape of an optical waveguide.
　光導波路を形成した基板１は、機械的強度を高めるため、直接接合又は樹脂等の接着層を介して、保持基板１１に接着固定される。直接接合する保持基板１１としては、光導波路や光導波路を形成した基板よりも屈折率が低く、光導波路などと熱膨張率が近い材料、例えば水晶やガラス、サファイヤ等の酸化物層を含む基板が好適に利用される。ＳＯＩ、ＬＮＯＩと略されるシリコン基板上に酸化ケイ素層を形成したものやＬＮ基板上に酸化ケイ素層を形成したその他の複合基板も利用可能である。
　なお、本発明における「光導波路基板」とは、「光導波路」や「光導波路を形成した基板」だけでなく、当該「保持基板」も含めた概念でもある。 The substrate 1 on which the optical waveguide is formed is adhesively fixed to the holding substrate 11 by direct bonding or via an adhesive layer such as resin, in order to increase mechanical strength. The holding substrate 11 to be directly bonded is made of a material that has a refractive index lower than that of the optical waveguide or the substrate on which the optical waveguide is formed and has a coefficient of thermal expansion close to that of the optical waveguide, such as a substrate containing an oxide layer such as crystal, glass, or sapphire. is suitably used. Other composite substrates such as SOI and LNOI, in which a silicon oxide layer is formed on a silicon substrate, and a silicon oxide layer formed on an LN substrate, can also be used.
Note that the "optical waveguide substrate" in the present invention includes not only an "optical waveguide" or a "substrate on which an optical waveguide is formed" but also the "holding substrate".
　例えば光導波路１０のモードフィールド径が３μｍ以下など光ファイバー等のモードフィールド径（約１０μｍ）と異なる場合には、図９及び１０などに示すように、スポットサイズ変換部ＳＳＣが形成される。本発明の光導波路素子に適用されるスポットサイズ変換部はこれらに限定されず、基板の端部に向かって徐々に光導波路の幅や高さが大きくなる、所謂、テーパー形状のスポットサイズ変換部であっても良い。なお、図９及び１０では、スポットサイズ変換部ＳＳＣはリブ型の光導波路１０の先端を幅が狭くなるテーパー形状とし、それを取り囲むようにコア部となるブロック部１００を配置した構成を例示している。
　また、図１０に示す、スポットサイズ変換部ＳＳＣの上面と補強部材（上部基板）２との距離ｈは、スポットサイズ変換部ＳＳＣのモードフィールド径の０．２倍から１．５倍に設定されている。 For example, when the mode field diameter of the optical waveguide 10 is 3 μm or less, which is different from the mode field diameter (approximately 10 μm) of an optical fiber, a spot size converter SSC is formed as shown in FIGS. 9 and 10. The spot size converter applied to the optical waveguide device of the present invention is not limited to these, but is a so-called tapered spot size converter in which the width and height of the optical waveguide gradually increases toward the edge of the substrate. It may be. In addition, in FIGS. 9 and 10, the spot size conversion unit SSC has a configuration in which the tip of the rib-shaped optical waveguide 10 has a tapered shape with a narrower width, and a block portion 100 serving as a core portion is arranged to surround it. ing.
Further, the distance h between the top surface of the spot size converter SSC and the reinforcing member (upper substrate) 2 shown in FIG. 10 is set to 0.2 to 1.5 times the mode field diameter of the spot size converter SSC. ing.
　本発明の光導波路素子では、光導波路（リブ型光導波路１０）又はスポットサイズ変換部ＳＳＣの上側には、補強部材２が配置される。補強部材２には、保持基板１１と同じ程度の屈折率や線膨張係数を有する材料が利用される。線膨張係数が一致していると、補強部材（上部基板）が熱応力で外れるなど不具合を低減することが可能となり、耐熱性に優れた光導波路素子が得られる。補強部材２と光導波路基板１又は保持基板１１とを接合する接着剤（接着層）３には、ＵＶ硬化樹脂や、アクリル系やエポキシ系等の樹脂などによる接着剤が使用可能である。 In the optical waveguide element of the present invention, the reinforcing member 2 is arranged above the optical waveguide (rib type optical waveguide 10) or the spot size converter SSC. For the reinforcing member 2, a material having the same refractive index and linear expansion coefficient as the holding substrate 11 is used. If the linear expansion coefficients match, it becomes possible to reduce defects such as the reinforcing member (upper substrate) coming off due to thermal stress, and an optical waveguide element with excellent heat resistance can be obtained. The adhesive (adhesive layer) 3 for bonding the reinforcing member 2 and the optical waveguide substrate 1 or the holding substrate 11 may be an adhesive made of a UV curing resin, an acrylic resin, an epoxy resin, or the like.
　本発明の光導波路素子の特徴は、光導波路基板１（１１）と補強部材２との接合強度を維持する第１の構造体ＳＴ１と、光導波路基板と補強部材との間の接着層の厚さを適切に設定するための第２の構造体ＳＴ２（ＳＴ２０～２２）とを少なくとも備えている。
　本実施例では第２の構造体ＳＴ２は第１の構造体ＳＴ１の上部に形成され、第２の構造体ＳＴ２の上面は第１の構造体ＳＴ１の上面より高い位置となるように形成されている。 The optical waveguide device of the present invention is characterized by the first structure ST1 that maintains the bonding strength between the optical waveguide substrate 1 (11) and the reinforcing member 2, and the thickness of the adhesive layer between the optical waveguide substrate and the reinforcing member. and a second structure ST2 (ST20 to ST22) for appropriately setting the height.
In this embodiment, the second structure ST2 is formed on the top of the first structure ST1, and the top surface of the second structure ST2 is formed at a higher position than the top surface of the first structure ST1. There is.
　第１の構造体ＳＴ１は、光導波路を挟むように配置され、特許文献１と同様に、スポットサイズ変換部ＳＳＣを含む光導波路を保護するための構造体として機能する。第１の構造体ＳＴ１は、当該第１の構造体と補強部材２との間に配置される接着層により、安定的な接合強度を確保する必要がある。このため、図７及び図９に示すように、補強部材２の下面の面積Ｓ０に対し、第１の構造体ＳＴ１の上面の面積の総和（Ｓ１＋Ｓ２）が占める割合が５０％以上であることが好ましい。なお、第１の構造体の上面の面積については、図７乃至１０に示すように、第１の構造体ＳＴ１の上面に第２の構造体ＳＴ２が配置されている部分の面積を除くことが好ましい。また、スポットサイズ変換部ＳＳＣのブロック部１００の高さが第１の構造体の高さと同じ程度であれば、第１の構造体の上面の面積の総和に加えることも可能である。 The first structure ST1 is arranged to sandwich the optical waveguide, and similarly to Patent Document 1, it functions as a structure for protecting the optical waveguide including the spot size converter SSC. The first structure ST1 needs to ensure stable bonding strength by the adhesive layer disposed between the first structure and the reinforcing member 2. Therefore, as shown in FIGS. 7 and 9, the ratio of the total area (S1+S2) of the top surface of the first structure ST1 to the area S0 of the bottom surface of the reinforcing member 2 is 50% or more. preferable. As for the area of the top surface of the first structure, as shown in FIGS. 7 to 10, it is possible to exclude the area of the portion where the second structure ST2 is arranged on the top surface of the first structure ST1. preferable. Furthermore, if the height of the block section 100 of the spot size conversion section SSC is approximately the same as the height of the first structure, it is possible to add it to the total area of the upper surface of the first structure.
　図８に示すように、光導波路１０の高さより第１の構造体ＳＴ１の高さを高くすることで、光導波路（スポットサイズ変換部の場合も同様）を保護する機能を第１の構造体に付与することが可能となるが、光導波路と第１の構造体との間、又は第１の構造体同士の間に気泡などが入り込み易くなることにも留意が必要である。 As shown in FIG. 8, by making the height of the first structure ST1 higher than the height of the optical waveguide 10, the function of protecting the optical waveguide (same in the case of the spot size converter) can be achieved by making the first structure ST1 higher than the height of the optical waveguide 10. However, it must be noted that air bubbles are likely to enter between the optical waveguide and the first structure or between the first structures.
　第２の構造体ＳＴ２も、光導波路を挟むように配置され、光導波路を挟む第２の構造体同士の間隔は、出来るだけ広く確保する方が、光導波路基板１（１１）と補強部材２との間隔を均一に保持する上では、好ましい。第２の構造体ＳＴ２は、専ら第１の構造体ＳＴ１と補強部材２との間隔Ｈを所定の範囲に保持するための役割を担っている。具体的には、所定の範囲は０．５μｍ以上、２．０μｍ以下である。また、光導波路１０（スポットサイズ変換部ＳＳＣ）と補強部材２との間隔ｈは、補強部材による伝搬光の損失を抑制するため、光導波路等のＭＦＤの０．２倍から１．５倍の範囲に設定することが好ましい。 The second structures ST2 are also arranged to sandwich the optical waveguide, and it is better to ensure as wide a gap as possible between the second structures sandwiching the optical waveguide between the optical waveguide substrate 1 (11) and the reinforcing member 2. This is preferable in order to maintain a uniform distance between the two. The second structure ST2 plays a role exclusively in maintaining the distance H between the first structure ST1 and the reinforcing member 2 within a predetermined range. Specifically, the predetermined range is 0.5 μm or more and 2.0 μm or less. In addition, the distance h between the optical waveguide 10 (spot size converter SSC) and the reinforcing member 2 is set to 0.2 to 1.5 times the MFD of the optical waveguide, etc., in order to suppress the loss of propagating light due to the reinforcing member. It is preferable to set it within a range.
　第２の構造体ＳＴ２は、第２の構造体の上端が補強部材２に接触するか、当該上端と補強部材２との間に接着剤が介在しても、その厚みは０．５μｍ未満に設定する。このため、第２の構造体の上面の面積は可能な限り小さく設定することが好ましい。第２の構造体ＳＴ２の数は、図７乃至１０に示すように、２個に限らず、後述するようにそれ以上配置しても良い。第２の構造体の横幅が大きく又は数が多い場合には、第２の構造体の機械的強度も高くなるため、図１０に示すような光導波路（スポットサイズ変換部ＳＳＣ）を保護する部材や第１の構造体ＳＴ１と補強部材２との間隔Ｈを所定の範囲に保持する部材として、より信頼性を高めることができる。 The thickness of the second structure ST2 is less than 0.5 μm even if the upper end of the second structure contacts the reinforcing member 2 or an adhesive is interposed between the upper end and the reinforcing member 2. Set. For this reason, it is preferable to set the area of the upper surface of the second structure to be as small as possible. The number of second structures ST2 is not limited to two as shown in FIGS. 7 to 10, and more may be arranged as described later. When the width of the second structure is large or the number of the second structures is large, the mechanical strength of the second structure is also high, so a member that protects the optical waveguide (spot size converter SSC) as shown in FIG. 10 is used. Also, reliability can be further improved as a member that maintains the distance H between the first structure ST1 and the reinforcing member 2 within a predetermined range.
　図７乃至図１０では、第１の構造体ＳＴ１の上側に第２の構造体ＳＴ２を積層する配置を示したが、本発明はこれに限らず、図１１乃至図１６に示すように、第１の構造体とは別に第２の構造体を配置することも可能である。 Although FIGS. 7 to 10 show the arrangement in which the second structure ST2 is stacked on top of the first structure ST1, the present invention is not limited to this, and as shown in FIGS. 11 to 16, It is also possible to arrange a second structure separately from the first structure.
　第２の構造体を第１の構造体から分離して配置する場合には、第１の構造体よりも外側に第２の構造体を配置し、第２の構造体同士の間隔は、出来るだけ広く確保する方が好ましい。なお、第１の構造体は、光導波路の両側に配置するだけでなく、片側にのみに配置しても良い。また、第１の構造体を光導波路と第２の構造体との間に配置するだけでなく、第２の構造体の外側（光導波路と反対側）に第１の構造体を配置しても良い。 When the second structure is placed separately from the first structure, the second structure is placed outside the first structure, and the distance between the second structures is as small as possible. It is preferable to secure as much space as possible. Note that the first structure may be placed not only on both sides of the optical waveguide, but also on only one side. Furthermore, in addition to arranging the first structure between the optical waveguide and the second structure, the first structure may be arranged outside the second structure (on the opposite side to the optical waveguide). Also good.
　第１及び第２の構造体を構成する材料としては、フォトレジスト（永久レジスト）などの樹脂材料が、多様な形状や配置に適しており、好適に利用可能である。また、光導波路素子の製造工程で使用する材料、例えば、光導波路基板１の一部、電極で使用される金などの導電材料、スポットサイズ変換部ＳＳＣのブロック部や、それ以外の光導波路の保護膜を構成する樹脂材料などを組み合わせて使用することも可能である。永久レジストに使用される樹脂として、ポリアミド系樹脂、メラミン系樹脂、フェノール系樹脂、アミノ系樹脂、エポキシ系樹脂など種々の材料を使用することが可能である。 As the material constituting the first and second structures, resin materials such as photoresists (permanent resists) are suitable for various shapes and arrangements, and can be suitably used. In addition, materials used in the manufacturing process of the optical waveguide device, such as a part of the optical waveguide substrate 1, a conductive material such as gold used in the electrodes, a block part of the spot size converter SSC, and other parts of the optical waveguide. It is also possible to use a combination of resin materials constituting the protective film. As the resin used for the permanent resist, various materials such as polyamide resin, melamine resin, phenol resin, amino resin, and epoxy resin can be used.
　第１及び第２の構造体を構成する材料の組み合わせとしては、図７乃至１０では、例えば、第１の構造体ＳＴ１に電極と同じ導電材料を使用し、第２の構造体ＳＴ２には、樹脂材料を使用した構成や、第１の構造体ＳＴ１と第２の構造体ＳＴ２の両方にフォトレジスト（永久レジスト）などの樹脂材料や電極と同じ導電材料を使用する構成とすることができる。
　また、上記以外の材料として光導波路基板１と同じ材料を用いてもよいし、石英やその他のガラス材料などを用いスパッタや蒸着など種々のプロセスで形成することもできる。 As a combination of materials constituting the first and second structures, in FIGS. 7 to 10, for example, the same conductive material as the electrode is used for the first structure ST1, and the same conductive material as the electrode is used for the second structure ST2. A configuration using a resin material, or a configuration using a resin material such as a photoresist (permanent resist) or the same conductive material as the electrodes for both the first structure ST1 and the second structure ST2 can be adopted.
In addition, the same material as the optical waveguide substrate 1 may be used as the material other than the above, or quartz or other glass materials may be used and formed by various processes such as sputtering or vapor deposition.
　図１１及び図１２では、第１の構造体ＳＴ１と第２の構造体を分離して構成しており、第１の構造体を、光導波路を被覆する保護膜（永久レジスト）と同じ材料、または、スポットサイズ変換部ＳＳＣのブロック部１００と同じ材料で形成することができる。また、第２の構造体は、電極材料と同じ材料で構成される部分ＳＴ２１にフォトレジスト材料で構成される部分ＳＴ２０との積層構造としている。 In FIGS. 11 and 12, the first structure ST1 and the second structure are configured separately, and the first structure is made of the same material as the protective film (permanent resist) that covers the optical waveguide. Alternatively, it can be formed of the same material as the block section 100 of the spot size conversion section SSC. Further, the second structure has a laminated structure in which a portion ST21 made of the same material as the electrode material and a portion ST20 made of a photoresist material.
　図１３及び図１４では、第２の構造体は、光導波路基板１の一部ＳＴ２２にフォトレジスト材料で構成される部分ＳＴ２０を積層した構造となっている。
　さらに、図１５及び図１６では、第２の構造体は、光導波路基板１の一部ＳＴ２２に電極材料で構成される部分ＳＴ２１を積層し、さらに、フォトレジスト材料で構成される部分ＳＴ２０を積層している。 In FIGS. 13 and 14, the second structure has a structure in which a portion ST20 made of a photoresist material is laminated on a portion ST22 of the optical waveguide substrate 1.
Furthermore, in FIGS. 15 and 16, the second structure has a portion ST21 made of an electrode material laminated on a portion ST22 of the optical waveguide substrate 1, and a portion ST20 made of a photoresist material is further laminated. are doing.
　図１１から図１６に示す実施例では第２の構造体ＳＴ２やＳＴ２０は第１の構造体ＳＴ１の上部ではなく構造体ＳＴ１の片側に別体として形成され、第２の構造体ＳＴ２やＳＴ２０の上面は第１の構造体ＳＴ１の上面より高い位置となるように形成されている。
　なお、図１１及び図１２における電極材料と同じ材料で構成される部分ＳＴ２１や図１３及び図１４における光導波路基板１の一部ＳＴ２２のそれぞれの高さがスポットサイズ変換部ＳＳＣの光導波路１０と同じ高さの場合、スポットサイズ変換部ＳＳＣのブロック部１００と第１の構造体ＳＴ１、及び第２の構造体であるフォトレジスト材料で構成される部分ＳＴ２０を同じ材料とし、同一の工程でそれぞれを同じ高さに形成してもよい。これにより製造プロセスを大幅に削減できるとともに、各構造体の高さのバラつきを抑制することができる。 In the embodiments shown in FIGS. 11 to 16, the second structures ST2 and ST20 are formed separately on one side of the structure ST1, not on the top of the first structure ST1, and the second structures ST2 and ST20 are formed separately on one side of the structure ST1. The upper surface is formed to be higher than the upper surface of the first structure ST1.
Note that the heights of the portion ST21 made of the same material as the electrode material in FIGS. 11 and 12 and the portion ST22 of the optical waveguide substrate 1 in FIGS. 13 and 14 are the same as those of the optical waveguide 10 of the spot size converter SSC. In the case of the same height, the block part 100 of the spot size conversion part SSC, the first structure ST1, and the part ST20 made of the photoresist material which is the second structure are made of the same material, and each is processed in the same process. may be formed at the same height. As a result, the manufacturing process can be significantly reduced, and variations in the height of each structure can be suppressed.
　図１７は、第１の構造体ＳＴ１の上に配置される第２の構造体ＳＴ２の配置のバリエーションを説明する図である。図１８は第１の構造体ＳＴ１とは分離して配置される第２の構造体（ＳＴ２０～２１）の配置のバリエーションを説明する図である。いずれの図も、補強部材の下部に位置する部分のみを抜き出して図示している。図１７の（ａ）及び図１８の（ａ）に示すように、光導波路の延在方向に沿って長く伸びる第２の構造体を形成することが可能である。長くなるのに従い、第２の構造体の機械的強度は高くなるが、２つの第２の構造体に挟まれる領域の接着層から気泡が図面の上下方向のみしか抜けないため、気泡が残留する可能性が高くなる。 FIG. 17 is a diagram illustrating variations in the arrangement of the second structure ST2 placed on the first structure ST1. FIG. 18 is a diagram illustrating variations in the arrangement of the second structures (ST20 and ST21) that are arranged separately from the first structure ST1. In both figures, only the portion located at the lower part of the reinforcing member is extracted and illustrated. As shown in FIGS. 17A and 18A, it is possible to form a second structure that extends long along the direction in which the optical waveguide extends. As the length increases, the mechanical strength of the second structure increases, but bubbles remain because the bubbles can only escape from the adhesive layer in the area sandwiched between the two second structures in the vertical direction of the drawing. More likely.
　図１７の（ｂ）及び図１８の（ｂ）に示すように、光導波路の延在方向に対して互い違いに配置することで、気泡が排出されるルートを確保しながら、補強部材の配置の安定性（ガタつき防止）も高くなる。図１７の（ｃ）及び図１８の（ｃ）の示すように、第２の構造体の長さを短くし、気泡の抜けだけでなく、第２の構造体と補強部材との間に配置される接着層を少なくし、気泡が残留するのを抑制することも可能となる。 As shown in FIG. 17(b) and FIG. 18(b), by arranging the reinforcing members alternately with respect to the extending direction of the optical waveguide, the reinforcing members can be arranged while ensuring a route for air bubbles to be discharged. Stability (wobble prevention) is also increased. As shown in FIG. 17(c) and FIG. 18(c), the length of the second structure is shortened, and the length of the second structure is not only removed, but also placed between the second structure and the reinforcing member. It is also possible to reduce the amount of adhesive layer used and to prevent air bubbles from remaining.
　これらのような構成は、補強部材を２つの第２の構造体のみで支持するため非常に不安定な構成に見えるが製造プロセスを工夫することでそれを解消することができる。例えば、複数の光導波路基板をウェハ上に配置する場合、ペアの光導波路基板におけるスポットサイズ変換部ＳＳＣ同士を向かい合うように配置して、２つのスポットサイズ変換部ＳＳＣに形成された合計４つの第２の構造体の上に補強部材を固定する。これにより補強部材は第２の構造体に安定して固定される。光導波路基板を切断する際は２つのスポットサイズ変換部ＳＳＣの中心を切断することでペアの光導波路基板を得ることができる。 Although these structures appear to be extremely unstable because the reinforcing member is supported only by the two second structures, this can be resolved by devising the manufacturing process. For example, when a plurality of optical waveguide substrates are arranged on a wafer, the spot size converters SSC of a pair of optical waveguide substrates are arranged so as to face each other, so that a total of four spot size converters SSC formed on the two spot size converters SSC are A reinforcing member is fixed on top of the second structure. Thereby, the reinforcing member is stably fixed to the second structure. When cutting the optical waveguide substrate, a pair of optical waveguide substrates can be obtained by cutting the centers of the two spot size converters SSC.
　第２の構造体の他のバリエーションとしては、図１９に示すように多数（光導波路の延在方向と直交方向の両方に複数）の第２の構造体を配置し、第２の構造体による補強部材の保持機能を高めることも可能である。ただし、第２の構造体間に気泡が留まることを避けるため、図面に示す以上に十分な間隔を確保することが好ましい。 As another variation of the second structure, as shown in FIG. It is also possible to enhance the holding function of the reinforcing member. However, in order to prevent air bubbles from remaining between the second structures, it is preferable to ensure a sufficient gap beyond that shown in the drawings.
　第２の構造体の数を、図２０では３個、図２１では４個、図２２では８個に設定した例を示している。通常、補強部材を支持する平面上に３点を確保することで、補強部材の配置は安定化するため、第２の構造体の上面の面積が小さい場合には、３個以上を配置することが好ましい。 An example is shown in which the number of second structures is set to three in FIG. 20, four in FIG. 21, and eight in FIG. 22. Normally, the placement of the reinforcing member is stabilized by securing three points on the plane that supports the reinforcing member, so if the area of the top surface of the second structure is small, it is recommended to arrange three or more reinforcing members. is preferred.
　本発明の光導波路素子は、光導波路基板１（１１）に光導波路１０を伝搬する光波を変調する変調電極を設け、図２３のように、筐体ＣＡ内に収容される。さらに、光導波路に光波を入出力する光ファイバー（Ｆ）を設けることで、光変調デバイスＭＤを構成することができる。図２３では、光ファイバーは、筐体の側壁を貫通する貫通孔を介して筐体内に導入し、光導波路素子に直接接合されている。光導波路素子と光ファイバーとは、空間光学系を介して光学的に接続することも可能である。 The optical waveguide element of the present invention is provided with a modulation electrode that modulates the light wave propagating through the optical waveguide 10 on the optical waveguide substrate 1 (11), and is housed in a housing CA as shown in FIG. 23. Furthermore, by providing an optical fiber (F) for inputting and outputting light waves to the optical waveguide, the optical modulation device MD can be configured. In FIG. 23, the optical fiber is introduced into the housing through a through hole penetrating the side wall of the housing, and is directly joined to the optical waveguide element. The optical waveguide element and the optical fiber can also be optically connected via a spatial optical system.
　光変調デバイスＭＤに変調動作を行わせる変調信号Ｓ０を出力する電子回路（デジタル信号プロセッサーＤＳＰ）を、光変調デバイスＭＤに接続することにより、光送信装置ＯＴＡを構成することが可能である。光導波路素子に印加する変調信号Ｓは増幅する必要があるため、ドライバ回路ＤＲＶが使用される。ドライバ回路ＤＲＶやデジタル信号プロセッサーＤＳＰは、筐体ＣＡの外部に配置することも可能であるが、筐体ＣＡ内に配置することも可能である。特に、ドライバ回路ＤＲＶを筐体内に配置することで、ドライバ回路からの変調信号の伝搬損失をより低減することが可能となる。 The optical transmitter OTA can be configured by connecting to the optical modulating device MD an electronic circuit (digital signal processor DSP) that outputs a modulation signal S0 that causes the optical modulating device MD to perform a modulation operation. Since the modulation signal S applied to the optical waveguide element needs to be amplified, a driver circuit DRV is used. The driver circuit DRV and the digital signal processor DSP can be placed outside the case CA, but they can also be placed inside the case CA. In particular, by arranging the driver circuit DRV within the housing, it becomes possible to further reduce the propagation loss of the modulated signal from the driver circuit.
　以上説明したように、本発明によれば、光導波路基板と補強部材との接合関係を適正に設定することが可能な光導波路素子を提供することが可能となる。また、その光導波路素子を用いた光変調デバイスと光送信装置を提供することが可能となる。 As described above, according to the present invention, it is possible to provide an optical waveguide element in which the bonding relationship between the optical waveguide substrate and the reinforcing member can be appropriately set. Furthermore, it is possible to provide an optical modulation device and an optical transmitter using the optical waveguide element.
　１　光導波路を形成する基板（薄板，膜体）
　２　補強部材
　ＡＤ　接着剤（接着層）
　１０　リブ型光導波路
　１１　保持基板（光導波路基板の一部）
　ＳＳＣ　スポットサイズ変換部
　ＳＴ１　第１の構造体
　ＳＴ２、ＳＴ２０～２２　第２の構造体
　ＬＢ　光学ブロック 1 Substrate (thin plate, film body) forming the optical waveguide
2 Reinforcement member AD Adhesive (adhesive layer)
10 Rib type optical waveguide 11 Holding substrate (part of optical waveguide substrate)
SSC Spot size converter ST1 First structure ST2, ST20-22 Second structure LB Optical block

Claims (10)

  1. 　光導波路を備えた光導波路基板と、該光導波路の端部付近で、該光導波路の上側に配置される補強部材と、該光導波路基板と該補強部材とは接着層を介して接合される光導波路素子において、
    　該光導波路基板と該補強部材との間には、該光導波路を挟むように複数の構造体が配置され、
    　第１の構造体は、該構造体の上面と該補強部材との間に接着層を配置し、該補強部材の下面の面積に対して該上面の面積が所定割合以上となるように設定され、
    　第２の構造体は、前記第１の構造体と該補強部材との間に配置される接着層の厚みを所定の範囲に設定するよう構成されていることを特徴とする光導波路素子。     An optical waveguide substrate including an optical waveguide, a reinforcing member disposed above the optical waveguide near an end of the optical waveguide, and the optical waveguide substrate and the reinforcing member are bonded via an adhesive layer. In optical waveguide devices,
    A plurality of structures are arranged between the optical waveguide substrate and the reinforcing member so as to sandwich the optical waveguide,
    The first structure has an adhesive layer disposed between the upper surface of the structure and the reinforcing member, and is set such that the area of the upper surface is at least a predetermined ratio to the area of the lower surface of the reinforcing member. ,
    An optical waveguide element, wherein the second structure is configured to set a thickness of an adhesive layer disposed between the first structure and the reinforcing member within a predetermined range.
  2. 　請求項１に記載の光導波路素子において、前記所定割合は５０％以上であることを特徴とする光導波路素子。 The optical waveguide device according to claim 1, wherein the predetermined ratio is 50% or more.
  3. 　請求項１又は２に記載の光導波路素子において、前記所定の範囲は０．５μｍ以上、２．０μｍ以下であることを特徴とする光導波路素子。 The optical waveguide element according to claim 1 or 2, wherein the predetermined range is 0.5 μm or more and 2.0 μm or less.
  4. 　請求項１に記載の光導波路素子において、前記第２の構造体は、前記第１の構造体の上に積層して配置されていることを特徴とする光導波路素子。 The optical waveguide device according to claim 1, wherein the second structure is arranged in a stacked manner on the first structure.
  5. 　請求項１に記載の光導波路素子において、該光導波路と前記第２の構造体との間に、前記第１の構造体の少なくとも一部が配置されていることを特徴とする光導波路素子。 The optical waveguide element according to claim 1, wherein at least a part of the first structure is disposed between the optical waveguide and the second structure.
  6. 　請求項１に記載の光導波路素子において、前記第２の構造体の上面の面積は、前記第１の構造体の上面の面積よりも小さいことを特徴とする光導波路素子。 The optical waveguide device according to claim 1, wherein the area of the top surface of the second structure is smaller than the area of the top surface of the first structure.
  7. 　請求項１に記載の光導波路素子において、該補強部材の下側に配置される該光導波路には、スポットサイズ変換部が形成されていることを特徴とする光導波路素子。 2. The optical waveguide element according to claim 1, wherein the optical waveguide arranged below the reinforcing member has a spot size conversion section formed therein.
  8. 　請求項１に記載の光導波路素子は、筐体内に収容され、該光導波路に光波を入力又は出力する光ファイバを備えることを特徴とする光変調デバイス。 The optical waveguide element according to claim 1 is an optical modulation device that is housed in a housing and includes an optical fiber that inputs or outputs a light wave to the optical waveguide.
  9. 　請求項８に記載の光変調デバイスにおいて、該光導波路素子は該光導波路を伝搬する光波を変調するための変調電極を備え、該光導波路素子の変調電極に入力する変調信号を増幅する電子回路を該筐体の内部に有することを特徴とする光変調デバイス。 9. The optical modulation device according to claim 8, wherein the optical waveguide element includes a modulation electrode for modulating a light wave propagating through the optical waveguide, and an electronic circuit that amplifies a modulation signal input to the modulation electrode of the optical waveguide element. An optical modulation device comprising: inside the housing.
  10. 　請求項８又は９に記載の光変調デバイスと、該光変調デバイスに変調動作を行わせる変調信号を出力する電子回路とを有することを特徴とする光送信装置。
          An optical transmitter comprising the optical modulation device according to claim 8 or 9 and an electronic circuit that outputs a modulation signal that causes the optical modulation device to perform a modulation operation.
PCT/JP2022/016659 2022-03-31 2022-03-31 Optical waveguide element, and optical modulation device and optical transmission device using same WO2023188311A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09105834A (en) * 1996-09-09 1997-04-22 Ngk Insulators Ltd Coupling structure for optical waveguide and optical fiber
US7076136B1 (en) * 2003-03-11 2006-07-11 Inplane Photonics, Inc. Method of attaching optical fibers to integrated optic chips that excludes all adhesive from the optical path
WO2008114657A1 (en) * 2007-03-16 2008-09-25 Omron Corporation Light transmission path package, light transmission module, electronic device and method for manufacturing light transmission module
JP2021162645A (en) * 2020-03-31 2021-10-11 住友大阪セメント株式会社 Optical waveguide element and optical modulation device including the same, and optical transmission device
JP2021162634A (en) * 2020-03-31 2021-10-11 住友大阪セメント株式会社 Optical waveguide element

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09105834A (en) * 1996-09-09 1997-04-22 Ngk Insulators Ltd Coupling structure for optical waveguide and optical fiber
US7076136B1 (en) * 2003-03-11 2006-07-11 Inplane Photonics, Inc. Method of attaching optical fibers to integrated optic chips that excludes all adhesive from the optical path
WO2008114657A1 (en) * 2007-03-16 2008-09-25 Omron Corporation Light transmission path package, light transmission module, electronic device and method for manufacturing light transmission module
JP2021162645A (en) * 2020-03-31 2021-10-11 住友大阪セメント株式会社 Optical waveguide element and optical modulation device including the same, and optical transmission device
JP2021162634A (en) * 2020-03-31 2021-10-11 住友大阪セメント株式会社 Optical waveguide element

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